Variable fin density coil

ABSTRACT

A heat exchanging coil that has at least one straight length of tube and at least one bend in the tube where fins are attached to the tube with unequal fin densities based upon tube orientation, and the fin density is different for straight lengths of tube than at bends in the tube.

RELATED APPLICATION

This application claims the benefit, and priority benefit, of U.S.provisional patent application Ser. No. 60/873,096, filed Dec. 6, 2006,entitled Variable Fin Density Coil.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to heat exchanging coils in air conditioningequipment, and more particularly to use of, manufacture of, or systemswith variable fin densities in lieu of constant fin densities on theheat-exchanging coils to reduce air flow restrictions at bends in theheat-exchanging coil to achieve greater efficiencies and cost savings.

2. Description of the Related Art

The use of heat-exchanging coils in air conditioning equipment is knownin the art as a means of transferring heat from inside of anair-conditioned space to an external heat sink, typically the outdoorenvironment. The heat-exchanging coil is made of one or more tubes thatare connected to allow a heat-exchanging medium to flow through thetubes.

The tubes have a series of protrusions, or fins, that are attached orsecured to the exterior of the tubes by various methods and generallyare disposed in planes substantially perpendicular to the longitudinalaxis of the tubes at the point of connection. The fins increase theconvective and conductive heat exchange as a fluid medium, typicallyair, is forced over the heat-exchanging coil by increasing the surfacearea for heat exchange between the heat-exchange medium inside of thetubes and the fluid medium passing over the tubes. The reason that thefins are typically disposed substantially perpendicular to thelongitudinal axis of the tubes at the point of contact is an attempt tominimize any restrictions in the fluid medium flow as it is forced overthe heat-exchanging coil.

The spacing, or fin density, of the fins along the tube is commonlyreferred to, or measured, as “fins per inch,” or generally the number offins along a one-inch length of tube. In prior art coils, the findensity is consistent, or constant, no matter the location on the tubewhere it is measured, i.e., on a straight section of tube or on a bendin the tube. The result is that the fins located on bends in theheat-exchanging coil tube tend to restrict the fluid medium flow overthe fins and the tube because the ends of the fins on the interiorradial surface of the tube come close to touching or actually touch,thus restricting, or impeding, the air flow between the fins. Thisrestriction in airflow caused by the fins at bends in the tube decreasesthe efficiency of the heat-exchanging coil, because the area of heatexchange is decreased due to the air restriction at the bend in thetube.

SUMMARY OF THE EMBODIMENTS OF THE INVENTION

An embodiment of the present invention relates to an improvedheat-exchanging coil design for air-conditioning equipment and themanufacturing of heat-exchanging coils for air-conditioning equipmentwherein variable fin densities are used depending upon the nature of aparticular section, or length, of the tube of the heat exchanging coil,e.g. a straight section, or length, of tube; a section having a bend orsharp curve; or a curved section defined by a relatively large radius ofcurvature.

The tube may be provided with a series of fins disposed substantiallyperpendicular to the longitudinal axis of the tube at the point ofconnection between the fin and the outer wall surface of the tube.Straight sections of tube may have a first fin density, while bends inthe tube may have a second fin density, and the first fin density may begreater than, or unequal to, the second fin density. Similarly, if thecoil is formed with bends and curved sections having relatively largeradii of curvature, the curved section may have a first fin density,while bends in the tube may have a second fin density, and the first findensity may be greater than, or unequal to, the second fin density. Thesecond fin density for the bends in the tube may be a constant densityor variable along the longitudinal axis of the tube. By using differentfin densities based upon the tube orientation, or location on the tube,i.e., straight section, curved section, or at a bend, improved heatexchange is achieved by reducing fluid medium flow restrictions. In aconstant fin density heat-exchanging coil, the fins at a bend tend totouch or come close to touching each other on one end, because the finsare perpendicular to the longitudinal axis of the tube at the point ofcontact.

An embodiment of the present invention relates to manufacturing ofheat-exchanging coils with variable fin densities employing variousmethods for securing fins to the tube. For example, fins may be attachedto a heat-exchanging coil tube by helically wrapping fins around thetube with either a first or second fin density. The wrapped fins maythen be secured by either a mechanical or welded fastening method.

An alternative method of attaching fins to the tube may includedisposing a series of fins along both straight sections of tube andbends in a tube at different densities. For example, a first fin densitymay be used on the straight lengths of tube, and a second fin densitymay be used at bends in the tube. Each of the fins may be provided witha fin collar that has a diameter that is greater than the initial outerdiameter of the tube at the outer wall surface of the tube. The fincollar with its enlarged diameter allows the fins to be disposed ateither a first or second fin density along the outer wall surface oftube. After the fins are disposed along the outer wall surface of tube,the tube may then be expanded from a first tube exterior diameter to asecond, enlarged or expanded, tube exterior diameter that is greaterthan the diameter of the fin collars. Because the diameter of the fincollars is smaller than the second tube exterior diameter, the finsdisposed along the tube at a first or second fin density are securedalong the outer wall surface of tube by a mechanical bond.

Another embodiment of the present invention relates to air conditioningsystems that utilize heat-exchanging coils with variable fin densities.Although any heat-exchanging coil in an air-conditioning system could bereplaced with a variable fin density heat-exchanging coil, in apreferred embodiment the condenser coil utilizes the variable findensity of the present invention.

Although common materials for constructing heat exchanging coils includealuminum and copper, any material that conducts heat could be used formaking a heat exchanging coil tube or fin. Since fewer fins are used atthe bends of the tube, cost savings are achieved, since less finmaterial is used.

These embodiments of manufacture, methods, and products of the presentinvention beneficially provide enhanced efficiencies and costs savingsbenefits over prior art coils by reducing air-flow restrictions at bendsin a coil, and by decreasing the amount of material used at a bend in acoil, or tube.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, advantages and features of the embodiments of the inventionwill become more apparent by reference to the drawings appended thereto,wherein like reference numerals indicate like parts, primed referencenumerals indicate parts of similar design, and wherein illustratedembodiments of the invention are shown, of which:

FIG. 1 is a schematic elevation view of a standard air conditioningsystem with a condensing unit located externally of the space being airconditioned;

FIG. 2 is a plan view of a portion of a coil tube with a straight lengthof tube and a bend in the tube and having a constant fin spacing densityfor both the straight length of tube and the bend in the tube, inaccordance with the prior art;

FIG. 3 is a plan view of a coil tube with a straight length of tube anda bend in the tube having a variable fin spacing density depending onthe tube orientation, in accordance with an embodiment of the presentinvention;

FIG. 4 is a plan view of a fin with a fin collar;

FIG. 5 is a perspective view of another coil, in accordance with anotherembodiment of the present invention; and

FIG. 6 is a plan view of the coil of FIG. 5.

While embodiments of the invention will be described in connection withthe preferred embodiments shown herein, it will be understood that it isnot intended to limit the invention to those embodiments. On thecontrary, it is intended to cover all alternatives, modifications, andequivalents, as may be included within the spirit and scope of theinvention as defined by the appended claims.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION

Referring to FIG. 1, a typical air conditioning system 10 is illustratedwherein the system 10 is broken into an interior unit 11 and an exteriorcondensing unit 15. The interior unit 11 includes at least one coolingcoil 12 and a fan 16. The interior unit 11 is connected to an air supplyductwork 20 having diffuser grilles 25 for distributing conditioned airinto the interior space 30. The interior unit 11 is also connected to areturn air inlet 35. The interior unit 11 may be provided with suitablecontrols to activate the interior unit 11 and to operate interior unit11 with exterior condensing unit 15. It should be understood by one ofordinary skill in the air conditioning field, that air conditioningsystem 10 may be of any type or design in that the embodiments hereindescribed may be used with any system 10 that has a coil 40, 40′, 40″ ashereinafter described.

The exterior condensing unit 15 is located in a heat sink 55 which istypically the outdoor environment, and typically includes at least onecondensing unit coil 40, a fan 45, a condensing unit compressor 50, andsuitable controls to operate exterior condensing unit 15 with theinterior unit 11, as are well known in the field of air conditioning.

Refrigeration tubing 60, 65 containing a refrigerant connects theinterior unit 11 and exterior condensing unit 15 to form a closed-loopsystem. The system functions by moving compressed refrigerant from theexterior condensing unit 15 to the interior unit 11 and allowing thecompressed refrigerant to expand, and then recompressing the refrigerantwith condensing unit compressor 50 at exterior condensing unit 15.

Heat from the interior space 30 is transferred to the refrigerant byforcing air from the interior space 30 over the cooling coil 12 by usingfan 16 to draw in air from interior space 30 through the return airinlet 35. The refrigerant then returns to the exterior condensing unit15 with the heat transferred to it from the interior space 30. The heatfrom the interior space 30 is then transferred to heat sink 55 byforcing a fluid medium, typically outside air, from heat sink 55 acrossthe condensing unit coil 40 with the aid of fan 45 and suitablecontrols.

Fan 45 can either draw air inwardly and downwardly from heat sink 55into the interior 41 of condenser 15, and outwardly over coil 40; or fan45 can draw air inwardly from heat sink 55 and across coil 40 and drawthe air outwardly and upwardly from interior 41 of condenser 15 to heatsink 55, as shown in FIG. 1. In either orientation of air flow, fan 45generally draws air flow over coil 40 at any given location on coil 40,as will be hereinafter described. The air flow is generally in adirection generally perpendicular to the longitudinal axis of the tubingof coil 40.

With reference to FIG. 2, a portion of a heat-exchanging coil 40(FIG. 1) according to the prior art is shown. Coil 40 may include one ormore tubes, or lengths of tubing, for the refrigerant to flow through.FIG. 2 shows, more specifically, a section, or portion, of a typicalheat-exchanging coil tube 70 having an outer wall surface 71 and havingboth straight sections, or lengths, 72 a, 72 b and a bend, or bendsection, 72 c. Bend 72 c has an exterior radial wall surface 74 definedby an outer radius of curvature R_(o) and an inner radial wall surface75 defined by an inner radius of curvature R_(i) wherein R_(o) isgenerally greater in length than R_(i).

As shown in FIG. 2, bend section 72 c is generally shown asapproximating a 90° bend, or elbow section, with the straight sections72 a, 72 b disposed approximately 90° to each other. The length oftubing 70 has a longitudinal axis 76, with the longitudinal axes ofsections 72 a, 72 b, and bend 72 c, appearing as 76 a, 76 b, and 76 c,respectively. The construction and shape or configuration of the coil40, will of course affect the actual angle present between the straightsections 72 a, 72 b and the bend section 72 c, or the angle formed bybend section 72 c. In the prior art, fins 77, as shown in FIG. 2, aredisposed at a constant fin density that is the same for both thestraight sections 72 a, 72 b and the bend section 72 c.

Fins 77 are disposed substantially perpendicular to the longitudinalaxes 76 a, 76 b, 76 c of tube 70 at the point of connection between anyfin 77 and tube 70, and are generally aligned with the airflow, as shownby arrows AF, over the sections 72 a, 72 b, 72 c of the tube 70. Forillustrative purposes and drawing clarity only, a limited number of fins77 are shown, it being readily apparent to one of ordinary skill in thisfield of technology that the fins are generally disposed over the entirelength of coil tube 70. In FIGS. 2 and 3 the direction of airflow A_(F)is illustrated, wherein fan 45 is drawing air inwardly and across coil40, and thereafter the air is forced outwardly and upwardly frominterior 41 of condenser 15, as shown in FIG. 1.

As shown in FIG. 2 the ends, or outer circumferential surface, 770 (FIG.4) of the fins 77 disposed along straight sections 72 a and 72 b of tube70 are generally equally spaced from each other so as to not impede airflow A_(F) passing over fins 77 and tube sections 72 a, 72 b. In generalfins 77 lie in planes which are substantially parallel with each otherand are typically spaced substantially an equal distance apart, wherebythe fins 77 are disposed on tube sections 72 a, 72 b with the same findensity.

Similarly the fins 77 disposed upon bend section 77 c in FIG. 2 have thesame fin density, but due to the presence of the bend, the ends 77, ofthe fins 77 disposed along the inner radial wall surface 75 of tubesection 72 c are much closer to each other and indeed may contact eachother at some locations, thereby obstructing airflow A_(F) over tubesection 72 c.

With reference to FIG. 3, a portion of a heat-exchanging coil tube 40′according to an embodiment of the present invention is shown, and mayinclude one or more tubes, or lengths or sections of tubing, for therefrigerant to flow through. FIG. 3 shows a section, or portion, of aheat-exchanging coil tube 70 having an outer wall surface 71 and havingboth straight sections or lengths 72 a, 72 b and a bend, or bend section72 c, in tube 70. Tube 70 may preferably be constructed of a heatexchanging material, such as copper or aluminum, although any materialhaving the requisite heat transfer and strength characteristics could beused. Fins 77 may be constructed of a heat exchanging material, such ascopper or aluminum. Fins 77 may be made of the same heat exchangingmaterial as tube 70, or may be a different heat exchanging material fromtube 70. Bend 72 c has an exterior radial wall surface 74 defined by anouter radius of curvature R_(o) and an inner radial wall surface 75defined by an inner radius of curvature R_(i) wherein R_(o) is generallygreater in length than R_(i).

As shown in FIG. 3, bend section 72 c is generally shown asapproximating a 90° bend, or elbow section, with the straight sections72 a, 72 b disposed approximately 90° to each other. The length oftubing 70 has a longitudinal axis 76, with the longitudinal axes ofsections 72 a, 72 b, and bend 72 c, appearing as 76 a, 76 b, and 76 c,respectively. The construction and shape or configuration of the coil40, will of course affect the angle present between the straightsections 72 a, 72 b and the bend section 72 c or the angle formed bybend section 72 c.

Fins 77 are disposed substantially perpendicular to the longitudinalaxis 76 a, 76 b, 76 c of tube 70 at the point of connection between anyfin 77 and tube 70, and the fins generally aligned with the airflow, asshown by arrows A_(F), over the sections 72 a, 72 b, 72 c of the tube70. For illustrative purposes and drawing clarity only, a limited numberof fins 77 are shown, it being readily apparent to one of ordinary skillin this field of technology that the fins are generally disposed overthe entire length of coil tube 70.

As shown in FIG. 3 the ends, or outer circumferential surface, 77 _(o)(FIG. 4) of the fins 77 disposed along straight sections 72 a and 72 bof tube 70 are generally equally spaced from each other so as to notimpede air flow A_(F) passing over fins 77 and tube sections 72 a, 72 b.In general fins 77 lie in planes which are substantially parallel witheach other and are spaced substantially an equal distance apart, wherebythe fins 77 are disposed on tube sections 72 a, 72 b with the same findensity, which may be considered, and defined, as a first fin density.

In FIG. 3, the fins 77 disposed upon bend section 72 c have a second findensity, the second fin density being different from the first findensity of the fins 77 secured to the sections 72 a, 72 b. The secondfin density is unequal to the first fin density, and preferably is lessthan the first fin density. Thus, there is a different density of fins77 disposed upon, or secured to, the outer wall surface 71 of the bendsection 72 c. Preferably, there are fewer fins on wall surface 71 of thebend section 72 c. As seen in FIG. 3, the ends 77 _(o) of the fins 77disposed along the inner radial wall surface 75 of tube section 72 _(c)are spaced apart from each other and do not contact each other, wherebyairflow A_(F) over and around the tube section 72 c is not obstructed,and airflow A_(F) may more freely flow over tube section 72 c.Additionally, if desired the second fin density of fins 77 disposed uponbend section, or sharp curve, 72 c may be a constant density, or it mayvary along the longitudinal axis of tube 70 within bend section 72 c.

The straight sections 72 a, 72 b of the tube 70 may have a first findensity that may be approximately between 14 and 24 fins per inch, andthe preferred first fin density is between 16 and 20 fins per inch. Thebend section 72 c in tube 70 has a second fin density that may beapproximately between 6 and 13 fins per inch, and the preferred secondfin density is between 8 to 13 fins per inch. By having two differentfin densities and varying the fin density based upon the location of thefins 77 on tube 70, the airflow across tube 70 at bend section 72 c isnot restricted to the same degree as the constant fin density spacingarrangement on tube 70, shown in FIG. 2.

To manufacture a tube 70 with two fin densities generally requires atube 70 that has at least one straight section 72 a or 72 b and one bendsection 72 c in the tube 70. Fins 77 are then disposed along the outerwall surface 71 of tube 70 at either a first or second fin densitydependent upon the location of the fins 77. Fins 77 are then attached totube 70. Fins 77 may be attached to the tube 70 by a variety of methods.One method of attaching, or securing, fins 77 to the tube 70, forexample, is by helically wrapping fins 77 around tube 70 at either afirst or second fin density based upon which section of the tube thefins will be attached, i.e. straight lengths 72 a or 72 b or bendsection 72 c. The fins 77 are then secured by either a mechanical orwelding fastening method to tube 70. Of course other fasteningtechniques and materials could be used such as epoxy bonding.

Another preferred method of attaching, or securing, fins 77 to tube 70is by disposing fins 77 along tube 70 at a first fin density where bothstraight sections 72 a, 72 b will occur, or be present, and disposingfins 77 upon tube 70 at a second fin density where the bend section 72 cwill occur, or be present, wherein fins 77 include a fin collar 95,shown in FIG. 4. Fin collar 95 has a diameter D_(F) that is greater thanthe initial outer diameter of tube 70 to allow fins 77 to be disposed ateither a first or second fin density along the outer wall surface 71 oftube 70. After the fins 77 are disposed along the outer wall surface 71of tube 70 at a first or second fin density based upon the orientationof the tube 70—straight or having a bend—tube 70 is then expanded fromits first original tube exterior diameter to a second enlarged orexpanded exterior diameter. The second diameter is greater, generallyslightly greater, than the diameter D_(F) of fin collars 95. Because thediameter D_(F) of fin collars 95 is smaller than the second enlargedexterior diameter, fins 77 are mechanically secured along the outer wallsurface 71 of tube 70. The tube is then bent, or otherwise suitablyformed, into its desired configuration, whereby the tube 70 has straightsections 72 a, 72 b and bend section 72 c.

A method of manufacturing a coil 40′ with a tube 70 for use inair-conditioning equipment comprises several steps. First, a tube 70,with an outer wall surface 71 with at least one straight length 72 a or72 b of tube 70 and at least one bend section 72 c in the tube 70, isprovided or utilized. Fins 77 are then disposed along the outer wallsurface 71 substantially perpendicular to the longitudinal axes (76 a,76 b, and 76 c) at the point of connection between fin 77 and the outerwall surface 71. The fins 77 are disposed at either a first or secondfind density based upon the orientation of tube 70, i.e. where thestraight sections 72 a, 72 b or bend section 72 c are to occur, or bepresent. The fin density for the straight sections 72 a and 72 b of tube70 is unequal to the fin density for fins 77 on bend section 72 c oftube 70. Preferably, the fin density for the straight sections 72 a and72 b of tube 70 is greater than the fin density for fins 77 on endsection 72 c of tube 70. The fins 77 may then be attached or secured totube 70 by one of the methods previously described or by other suitablefastening methods. The tube 70 may then be bent, or otherwise suitablyformed, into the desired configuration, whereby the tube 70 has straightsections 72 a, 72 b and bend section 72 c.

With reference to FIGS. 5 and 6, a portion of a heat-exchanging coiltube 40″ according to an embodiment of the present invention is shown,and may include one or more tubes, or lengths of sections of tubing forthe refrigerant to flow through, 70′. The construction of coil 40″includes a plurality of heat-exchanging coil tubes 70′, and coil 40″ issubstantially of the same construction and design as that previouslydescribed in connection with FIGS. 1, 3 and 4. The tubes 70′ of coil 40″include bends, or bend sections, 72 c having an outer radius ofcurvature R_(o) and an inner radius of curvature R_(i), wherein R_(o) isgenerally greater in length than R_(i). The embodiment of coil 40″ ofFIGS. 5 and 6 differs from coil 40′ of FIG. 3 in that instead of havingstraight sections, or lengths, 72 a, 72 b, as shown in FIG. 3, coil 40″includes curved sections, or lengths, 72′a and 72′b which are defined byrelatively large radii of curvature R′_(o) and R′_(i) which define theexterior radial wall surface and interior radial wall surfaces of curvesection 72′a and 72′b. Again, the outer radius of curvature R′_(o) isgenerally greater in length than the inner radius of curvature R′_(i).Fins 77 may be attached, or otherwise suitably secured to tubes 70′ inthe manner previously described in connection with FIGS. 3 and 4,including utilizing unequal fin densities for bend sections 72 c andsections 72′a and 72′b.

As seen in FIGS. 5 and 6, curve section 72′a and 72′b approximatestraight sections 72 a and 72 b of FIG. 3. Thus, as used in the claimsappended hereto, the use of the term “straight section” is defined toinclude both straight sections 72 a, 72 b, and curved sections 72′a and72′b. The method of manufacturing coil 40″ may differ from thatpreviously described in connection with coil 40′ in that as the tube 70′is bent, or otherwise suitably formed, into the desired configurationwhereby the tube 70′ has bend section 72 c, it is also bent, orotherwise suitably formed, into the desired configuration, whereby thetube 70′ has curved sections 72′a, and 72′b.

Having described certain embodiments of the invention, variousmodifications and changes of the techniques, procedures, components andequipment will be apparent to those skilled in the art. It is intendedthat all such variations within the scope and spirit of the appendedclaims be embraced thereby.

1. A coil for air-conditioning equipment, comprising: at least one tubehaving an outer wall surface, the at least one tube including at leastone substantially straight section and at least one bend section; the atleast one tube having a plurality of fins attached to the outer wallsurface of the at least one tube; the fins being disposed in a spacedrelationship from adjacent fins along the outer wall surface of the atleast one tube; the fins disposed along the at least one straightsection having a first fin density; the fins disposed along the bendsection having a second fin density; and the first fin density isunequal to the second fin density.
 2. The coil of claim 1, wherein thefirst fin density is greater than the second fin density.
 3. The coil ofclaim 1, wherein the first fin density is less than the second findensity.
 4. The coil of claim 1, wherein the first fin density isapproximately between 14 to 24 fins per inch, and the second fin densityis approximately between 6 to 13 fins per inch.
 5. The coil of claim 4,wherein the first fin density is approximately between 16 to 20 fins perinch, and the second fin density is approximately between 8 to 13 finsper inch.
 6. The coil of claim 1, wherein the bend section in the atleast one tube forms an angle approximately between 60 and 179 degrees.7. The coil of claim 6, wherein the bend section in the at least onetube forms an angle between 90 and 120 degrees.
 8. The coil of claim 1,wherein the fins are constructed from a heat conducting material, andthe same heat conducting material is used for the at least one tube. 9.The coil of claim 1, wherein the fins are constructed from a differentheat conducting material and the at least one tube is made of adifferent heat conducting material.
 10. The coil of claim 1, wherein theat least one tube is made of copper or aluminum.
 11. The coil of claim10, wherein the fins are made of copper or aluminum.
 12. The coil ofclaim 1, wherein the fins are wrapped around the outer wall surface ofthe at least one tube.
 13. The coil of claim 1, wherein the fins includea fin collar having an interior diameter.
 14. A method of manufacturinga coil for use in air-conditioning equipment, comprising the steps of:providing at least one tube having an outer wall surface, the at leastone tube to have at least one straight section and at least one bendsection; attaching a first plurality of fins at a first fin density uponthe outer wall surface of the at least one tube where the at least onestraight section will be present; attaching a second plurality of finsat a second fin density upon the outer wall surface of the at least onetube where the at least one bend section will be present; and utilizinga first fin density that is unequal to the second fin density.
 15. Themethod of claim 14, wherein the first fin density is greater than thesecond fin density.
 16. The method of claim 14, wherein the first findensity is less than the second fin density.
 17. The method of claim 16,wherein the first fin density is approximately between 14 to 24 fins perinch, and the second fin density is approximately between 6 to 13 finsper inch.
 18. The method of claim 17, wherein the first fin density isapproximately between 16 to 20 fins per inch, and the second fin densityis approximately between 8 to 13 fins per inch.
 19. The method of claim16, wherein the fins are attached by wrapping the fins around the outerwall surface of the at least one tube.
 20. The method of claim 16,wherein at least some of the fins have a fin collar having a fin collarinterior diameter and the at least one tube has a first exteriordiameter, which diameter is smaller than the fin collar interiordiameter; including the steps of: expanding the at least one tube untilthe at least one tube has a second expanded diameter, and the secondexpanded diameter is greater than fin collar interior diameter.
 21. Anair-conditioning condenser unit, comprising: a housing; a compressoradapted to compress a refrigerant; a condenser coil including at leastone tube having an outer wall surface, the at least one tube having atleast one straight section and at least one bend section; a plurality offins attached to the outer wall surface of the at least one tube, thefins being disposed in a spaced relationship from adjacent fins alongthe outer wall surface of the at least one tube; the fins disposed alongthe at least one straight section having a first fin density; the finsdisposed along the at least one bend section having a second findensity; the first fin density being unequal to the second fin density;and a fan for drawing air across the condenser coil.
 22. Theair-conditioning condenser unit of claim 21, wherein the first findensity is greater than the second fin density.
 23. The air-conditioningcondenser unit of claim 21, wherein the first fin density is less thanthe second fin density.
 24. The air-conditioning condenser unit of claim21, wherein the first fin density is approximately between 14 to 24 finsper inch, and the second fin density is approximately between 8 to 13fins per inch.
 25. The air-conditioning condenser unit of claim 24,wherein the first fin density is approximately between 16 to 20 fins perinch, and the second fin density is approximately between 9 to 13 finsper inch.